Exploring window buffer layer technology to enhance CdTe solar cell performance. (April 2018)

• Record Type: Journal Article
• Authors: Wang, Taowen; Ren, Shengqiang; Li, Chunxiu; Li, Wei; Liu, Cai; Zhang, Jingquan; Wu, Lili; Li, Bing; Zeng, Guanggen
• Is Part Of: Solar energy. Volume 164(2018)
• Page Start: 180
• Page End: 186
• Publication Date: 2018-04
• Subjects: QE response -- Window buffer layer -- Build-in potential -- CdTe solar cells; Solar energy -- Periodicals; Solar engines -- Periodicals; 621.47
• DOI: 10.1016/j.solener.2018.02.044
• Languages: English
• ISSNs: 0038-092X

Abstract

Highlights: MZO/CdTe solar cells with window buffer layers were fabricated. The solar cells were characterized by combined techniques such as Bias-QE, MCE, JV, CV. Theoretical simulations indicate that cell performance is strongly correlated with the built-in potential. The incorporation of the window buffer layer is a variable method to increase the built-in potential in MZO/CdTe solar cells. Abstract: The short-wavelength response for traditional CdS/CdTe thin film solar cells was dramatically restricted by the CdS window layer. In order to increase short-wavelength light collection, we tried to replace CdS with Mgx Zn1−x O (MZO). The short-wavelength quantum efficiency ( QE ) response was obviously increased to more than 80% at 400 nm, while fill factor (FF) and open circuit voltage ( Voc ) for CdTe solar cells were decreased. This decrease was mainly caused by the weak build-in potential formed by the MZO/CdTe heterojunction, which resulted in insufficient driving force to repel the photo-generated carriers. Hence, the thin CdS buffer layer was introduced between MZO and CdTe to improve the built-in potential. It efficiently increased the build-in potential from 0.369 to 0.579 V with an obvious improvement of FF and Voc . But this interlayer caused QE losses to some degree in the short-wavelength region. To avoid these losses, a composite CdS/CdSe buffer layer was incorporated in the CdTe solar cells. CdSe acted as a protective layer to avoid the excessive CdS consumption during the high temperature deposition processing of the CdTe absorption layer. Meanwhile the formation of CdSex Te1−x by inter-diffusion extended the long-wavelength response. Thus, cell performance was enhanced with a relatively high build-in potential 0.517 V and a substantial improvement of the QE response.